Fluid flow measurement and control

ABSTRACT

In accordance with another embodiment, a controller in a fluid delivery system initiates drawing fluid into a chamber of a diaphragm pump. During a delivery phase of pumping the fluid in the chamber to a target recipient, the controller applies pressure to the chamber. At multiple different times during the delivery phase, the controller temporarily discontinues application of the pressure to the chamber to calculate how much of the fluid in the chamber has been pumped to the target recipient.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/761,109 entitled “Measurement and Control ofFluid Flow in an Intravenous Pump,” filed on Feb. 5, 2013, the entireteachings of which are incorporated herein by this reference.

BACKGROUND

Conventional techniques of delivering fluid to a recipient can includedrawing a fluid from a fluid source into a chamber of a diaphragm pump.After the chamber is filled, a respective fluid delivery system appliesa pressure to the chamber causing the fluid in the chamber to bedelivered to a corresponding patient. The rate at which the fluid isdelivered to the recipient may vary depending upon the magnitude ofpressure applied to the chamber.

Eventually, after applying pressure to the chamber for a sufficientamount of time, all of the fluid in the chamber is delivered to therecipient.

In most applications, the amount of fluid drawn into the chamber of thediaphragm pump is substantially less than the amount of fluid to bedelivered to the patient. To deliver the appropriate amount of fluid tothe patient over time, the fluid delivery system repeats the cycle ofdrawing fluid from the fluid source into the chamber, and then applyingpressure to the chamber to deliver the fluid to the recipient.

According to conventional techniques, based on the amount of elapsedtime between time successive operations of drawing fluid into andexpelling the fluid out of the chamber in the diaphragm pump, the fluiddelivery system is able to determine the rate at which fluid isdelivered to a corresponding patient.

BRIEF DESCRIPTION OF EMBODIMENTS

Embodiments herein are novel over conventional methods.

Temperature Estimation and Control

More specifically, in accordance with first embodiments, a fluiddelivery system includes a first volume (such as a first chamber) and asecond volume (such as a second chamber). Assume that the first volumeis of a known magnitude and that the second volume is of an unknownmagnitude. In one embodiment, a controller in the fluid delivery systemcontrols magnitudes of pressures in the first volume and the secondvolume to deliver fluid to a corresponding recipient.

To produce a more accurate measurement of fluid delivered to arecipient, the controller estimates a temperature of gas in the firstvolume and a temperature of gas in the second volume. The controllerestimates the temperatures based on measurements of pressure in thefirst volume and measurements of pressure in the second volume. In otherwords, in one embodiment, the controller derives the estimated gastemperatures at least in part from the measurement of pressures in thefirst volume and the second volume.

In addition to estimating temperatures, the controller as describedherein can be configured to calculate a magnitude of the second volumebased on a combination of measured pressures and estimated temperaturesof the gases in the first volume and the second volume.

In accordance with further embodiments, the fluid delivery system asdescribed herein includes a valve disposed between the first volume andthe second volume. The controller of the fluid delivery system initiallycloses the valve to prevent a transfer of gas between the first volumeand the second volume. While the valve is closed, the controllercontrols a pressure of the first volume to be substantially dissimilarto a pressure of the second volume. During a measurement cycle ofdetermining a size of the second volume, the controller opens the valvebetween the first volume and the second volume to enable a transfer ofgas and to equalize the first volume and the second volume tosubstantially the same pressure. In accordance with further embodiments,the controller calculates the magnitude of the second volume based atleast in part on measured pressures of the gases before and afteropening the valve.

Thermal effects of the first volume and/or the second volume can have animpact on calculated volume. In accordance with yet further embodiments,to estimate the temperature of gas in the first volume and thetemperature of gas in the second volume, the controller derives theestimated temperature of the gas in the first volume and the estimatedtemperature of the gas in the second volume based at least in part onthermal effects due to changes in pressure of the gases in the firstvolume and the second volume.

Physical attributes of the first volume and the second volume can affectrespective actual and estimated gas temperatures of the gases. Inaccordance with further embodiments, when estimating the temperature ofgas in the first volume and the temperature of gas in the second volume,the controller can be configured to derive the temperature of the gas inthe first volume and the temperature of the gas in the second volumebased at least in part on an estimated transfer of heat between thegases and respective physical boundaries defining the first volume andthe second volume.

By further way of non-limiting example, note that the second volume canbe a first chamber in a diaphragm pump. The diaphragm pump can include asecond chamber disposed adjacent the first chamber. A flexible membranein the diaphragm pump defines a boundary between the first chamber andsecond chamber. The controller controls a pressure applied to the firstchamber (the second volume) to pump fluid in the second chamber to atarget recipient. As described herein, the controller can apply negativepressure to the second volume to decrease a size of the second volume,drawing fluid into the second chamber of the diaphragm pump. Thecontroller can apply positive pressure to the first chamber (secondvolume) to expel fluid from the second chamber of the diaphragm pump toa corresponding downstream recipient.

In accordance with still further embodiments, when the controllerapplies positive pressure to the second volume, the second volumechanges over time as a result of delivering the fluid to the recipient.When estimating the temperature of gas in the first volume and thetemperature of gas in the second volume, the controller can beconfigured to derive the temperature of the gas in the first volume andthe temperature of the gas in the second volume based at least in parton a calculated change in the second volume over time.

In further embodiments, the controller uses the calculated magnitude ofthe second volume (volume of the first chamber in the diaphragm pump) todetermine a flow rate of delivering fluid from the second chamber of thediaphragm pump to the target recipient.

Discontinuous Control Operation

In accordance with second embodiments, a controller in a fluid deliverysystem initiates drawing fluid into a chamber of a diaphragm pump.During a delivery phase, the controller applies positive pressure to thechamber. The applied positive pressure pumps the fluid in the chamber toa target recipient. At one or more times during the delivery phase, thecontroller temporarily discontinues or interrupts application of apressure to the chamber to calculate how much of the fluid in thechamber has been pumped to the target recipient.

More specifically, assume that the fluid delivery system first initiatesfilling a chamber in a diaphragm pump. The fluid delivery system exertspressure on the chamber to deliver a portion of the fluid in thediaphragm pump to a downstream recipient. The fluid delivery systemtemporarily discontinues application of pressure to the chamber. In oneembodiment, discontinuing application of the pressure includes reducinga pressure applied to the chamber. The reduced pressure causes pumpingof the fluid in the chamber to the recipient to slow down or stop for ashort amount of time. The time of the interruption of pressure may be soshort that it is unnoticeable or insignificant.

During such time of temporarily discontinuing application of a pressure,the fluid delivery system calculates the amount of the fluid remainingin the chamber of the diaphragm pump.

After calculating the amount of fluid remaining in the chamber, thefluid delivery system applies pressure to the chamber again,(potentially the same or substantially similar pressure applied prior tothe interruption) causing the fluid in the chamber to resume normaldelivery of fluid to the recipient. In other words, resumption ofapplying the pressure to the chamber causes the fluid in the chamber toflow again to the recipient.

In one embodiment, the fluid delivery system repeats this process ofdiscontinuing application of the pressure to the chamber to calculate anamount of fluid remaining in the chamber multiple times during adelivery phase. Multiple measurements enables the fluid delivery systemto accurately detect an amount or flow of fluid to a recipient overtime.

In yet further embodiments, as mentioned, the controller can beconfigured to apply a substantially constant pressure (before and aftera step of temporarily discontinuing application of pressure) to thechamber to evacuate the fluid from the chamber into a respective conduitthat conveys the fluid to the target recipient.

Using the calculated amount of fluid remaining in the chamber atdifferent times during the delivery phase, the controller can calculatea flow rate of delivering the fluid in the chamber to the targetrecipient.

In accordance with further embodiments, the controller can be configuredto compare the calculated flow rate to a desired flow rate such as a setpoint. In response to detecting that a difference between the calculatedflow rate and the desired flow rate is greater than a threshold value,the controller can be configured to adjust a flow rate of the fluid fromthe chamber to the target recipient to be nearer to the desired flowrate.

Note that the controller can modify any suitable control parameter toadjust a flow rate of the fluid if it is different than a respectivedesired set point. For example, in one embodiment, the controlleradjusts a magnitude of the pressure applied to the chamber during thedelivery phase to increase or decrease the fluid delivery rate.Additionally or alternatively, the controller can be configured toadjust resistance of an in-line fluid flow resistor disposed between thechamber and the target recipient.

Discontinuing application of the drive pressure to the chamber caninclude controlling magnitudes of pressure in the chamber and a gasreservoir tank to be dissimilar. The reservoir tank can be a volume ofknown magnitude; the chamber can be a volume of unknown magnitude. Inother words, as mentioned, the chamber can represent a varying volume, amagnitude of which varies as fluid is delivered to a recipient.

In further embodiments, the controller opens a valve between thereservoir tank and the chamber to substantially equalize a pressure ofgas in the reservoir tank and the chamber. To more accurately calculatea rate of fluid delivery, as previously discussed, the controller can beconfigured to estimate a temperature of gas in the reservoir tank and atemperature of gas in the chamber based on a measured pressure in thereservoir tank and measured pressure of the chamber. The controllercalculates how much fluid remains in the chamber based at least in parton measured pressures of the gases and the estimated temperatures of thegases in the reservoir tank and the chamber.

Also, as previously mentioned, the controller can be configured tocalculate how much of the fluid has been pumped to the target recipientbased at least in part on how much of the fluid drawn into the chamberremains in the chamber after applying positive pressure to the diaphragmpump.

These and other more specific embodiments are disclosed in more detailbelow.

Note that any of the resources as discussed herein can include one ormore computerized devices, fluid delivery systems, servers, basestations, wireless communication equipment, communication managementsystems, workstations, handheld or laptop computers, or the like tocarry out and/or support any or all of the method operations disclosedherein. In other words, one or more computerized devices or processorscan be programmed and/or configured to operate as explained herein tocarry out different embodiments of the invention.

Yet other embodiments herein include software programs to perform thesteps and operations summarized above and disclosed in detail below. Onesuch embodiment comprises a computer program product including anon-transitory computer-readable storage medium (i.e., any physicalcomputer readable hardware storage medium) on which softwareinstructions are encoded for subsequent execution. The instructions,when executed in a computerized device (e.g., computer processinghardware) having a processor, program and/or cause the processor toperform the operations disclosed herein. Such arrangements are typicallyprovided as software, code, instructions, and/or other data (e.g., datastructures) arranged or encoded on a non-transitory computer readablestorage medium such as an optical medium (e.g., CD-ROM), floppy disk,hard disk, memory stick, etc., or other a medium such as firmware orshortcode in one or more ROM, RAM, PROM, etc., or as an ApplicationSpecific Integrated Circuit (ASIC), etc. The software or firmware orother such configurations can be installed onto a computerized device tocause the computerized device to perform the techniques explainedherein.

Accordingly, embodiments herein are directed to a method, system,computer program product, etc., that supports operations as discussedherein.

One embodiment herein includes a computer readable storage medium and/orsystem having instructions stored thereon. The instructions, whenexecuted by computer processor hardware, cause the computer processorhardware to: control magnitudes of pressure in a first volume and asecond volume, the first volume being of a known magnitude, the secondvolume being of an unknown magnitude; estimate a temperature of gas inthe first volume and a temperature of gas in the second volume based onmeasurements of pressure in the first volume and measurements ofpressure in the second volume; and calculate a magnitude of the secondvolume based on measured pressures of the gases and estimatedtemperatures of gases in the first volume and the second volume.

Another embodiment herein includes a computer readable storage mediumand/or system having instructions stored thereon. The instructions, whenexecuted by computer processor hardware, cause the computer processorhardware to: initiate drawing fluid into a chamber of a diaphragm pump;during a delivery phase of pumping the fluid in the chamber to a targetrecipient, applying pressure to the chamber; and at multiple differenttimes during the delivery phase, temporarily discontinuing applicationof the pressure to the chamber to calculate how much of the fluid in thechamber has been pumped to the target recipient.

Yet another embodiment herein includes a computer readable storagemedium and/or system having instructions stored thereon. Theinstructions, when executed by computer processor hardware, cause thecomputer processor hardware to: control magnitudes of pressure in afirst volume and a second volume to be dissimilar, the first volumebeing of a known magnitude, the second volume being of an unknownmagnitude; initiate opening a valve between the first volume and thesecond volume to equalize a pressure in the first volume and the secondvolume; estimate a temperature of gas in the first volume and atemperature of gas in the second volume based on a measured pressure inthe first volume and measured pressure of the second volume; andcalculate a magnitude of the second volume based on measured pressuresof the gases and estimated temperatures of the gases in the first volumeand the second volume.

The ordering of the operations above has been added for clarity sake.Note that any of the processing steps as discussed herein can beperformed in any suitable order.

Other embodiments of the present disclosure include software programsand/or respective hardware to perform any of the method embodiment stepsand operations summarized above and disclosed in detail below.

It is to be understood that the system, method, apparatus, instructionson computer readable storage media, etc., as discussed herein also canbe embodied strictly as a software program, firmware, as a hybrid ofsoftware, hardware and/or firmware, or as hardware alone such as withina processor, or within an operating system or within a softwareapplication.

As discussed herein, techniques herein are well suited for use indelivering fluid to a recipient. However, it should be noted thatembodiments herein are not limited to use in such applications and thatthe techniques discussed herein are well suited for other applicationsas well.

Additionally, note that although each of the different features,techniques, configurations, etc., herein may be discussed in differentplaces of this disclosure, it is intended, where suitable, that each ofthe concepts can optionally be executed independently of each other orin combination with each other. Accordingly, the one or more presentinventions as described herein can be embodied and viewed in manydifferent ways.

Also, note that this preliminary discussion of embodiments hereinpurposefully does not specify every embodiment and/or incrementallynovel aspect of the present disclosure or claimed invention(s). Instead,this brief description only presents general embodiments andcorresponding points of novelty over conventional techniques. Foradditional details and/or possible perspectives (permutations) of theinvention(s), the reader is directed to the Detailed Description sectionand corresponding figures of the present disclosure as further discussedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example diagram illustrating a fluid delivery systemaccording to embodiments herein.

FIG. 2 is an example diagram illustrating more specific details ofcomponents and partitioning in a fluid delivery system according toembodiments herein.

FIG. 3 is an example diagram illustrating details of a diaphragm pumpused in a fluid delivery system according to embodiments herein.

FIG. 4 is an example diagram illustrating a change in hypothetical gastemperatures during a fluid measurement cycle according to embodimentsherein.

FIG. 5A is an example timing diagram illustrating application ofdifferent pressure to a diaphragm pump over time to deliver fluid to atarget recipient according to embodiments herein.

FIG. 5B is an example timing diagram illustrating application ofdifferent pressure to a diaphragm pump over time to deliver fluid to atarget recipient according to embodiments herein.

FIG. 6 is an example timing diagram illustrating temporary terminationor reduction of applying positive pressure to a diaphragm pump andestimation of gas temperatures according to embodiments herein.

FIG. 7 is a diagram illustrating an example computer architecture inwhich to execute any of the functionality according to embodimentsherein.

FIGS. 8-10 are example diagrams illustrating methods facilitating flowcontrol measurement and management according to embodiments herein.

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments herein, as illustrated in theaccompanying drawings in which like reference characters refer to thesame parts throughout the different views. The drawings are notnecessarily to scale, with emphasis instead being placed uponillustrating the embodiments, principles, concepts, etc.

DETAILED DESCRIPTION AND FURTHER SUMMARY OF EMBODIMENTS

The fluid delivery system as described herein uses a system of valves,variable flow restrictions, reference volumes, direct pressuremeasurements, etc., to accurately deliver intravenous fluids to arecipient such as a patient. Typically fluids are introduced to thepatient through a vein in the hand or arm. The pressure in the vein istypically on the order of 5 mm of Hg above atmosphere.

Conventional fluid pumps currently available in the market require thata respective fluid source be in a prescribed location with respect tothe pump. Likewise, the pump must be in a prescribed location withrespect to the patient. Variation in either source location or patientlocation can cause flow rate inaccuracy due to the affects of systempressure on the pumping mechanism. It is desirable for many reasons in aclinical setting for the pump to be able to deliver the fluid to thepatient irrespective of the source fluid and pump position.

Embodiments herein use compressed gas (air) to induce the requireddifferential pressures needed to move the fluid into the patient under awide range of relative positions of the pump, the patient, and the fluidsource. The fluid to be delivered may be below the patient or above thepatient. The pump may be above or below the patient regardless of thefluid location. In certain instances, it is desirable that the fluid bedelivered at as low a pressure as possible and at a continuous flowrate. The pump is able to use low pressure and accommodate a variety ofrelative pump and/or patient positions because the system can measureflow rate and adjust for any variations away from the target flow rate.

There are primarily two types of IV pumps on the market today; syringeand linear peristaltic pumps. Both are positive displacement pumps,which can present very high pressures to the patient in manycircumstances. There are many limitations of this technology. As anexample, in order to mitigate this risk, pressure sensors are added todetect dangerously high pressures and stop the pump. Due to theconfiguration of this technology and the elasticity of the tubing, largeboluses of fluid are often injected to the patient inadvertently. Incontrast, by using drive pressure directly to push the fluid to thepatient rather than a rigid mechanical piston any disturbances stop thepump directly without the need for a detection system.

Now, more specifically, FIG. 1 is an example diagram illustrating afluid delivery system according to embodiments herein.

As shown, fluid delivery environment 101 includes fluid delivery system100. Fluid delivery system 100 includes fluid source 120-1, fluid source120-2, and recipient 108. Fluid delivery system 100 includes controller140 as well as cassette 104, facilitating delivery of fluid from one ormore fluid sources 120 to the recipient 108.

In one embodiment, the cassette 104 is a disposable cartridge insertedinto a cavity of a housing of the fluid delivery system 100. Duringdelivery, fluid from the different fluid sources 120 is limited tocontacting (disposable tube set including) cassette 104, tubes 103, andits corresponding components as further discussed below. When deliveringfluid to a different patient, a caregiver inserts a new cassette intothe cavity of fluid delivery system 100. The new cassette includes acorresponding set of new (sterile) tubes. Thus, the fluid deliverysystem 100 can be used for many patients without having to be cleaned.

As mentioned, during operation, the controller 140 of fluid deliverysystem 100 controls delivery of fluid from one or more fluid sources 120(such as fluid source 120-1 and/or fluid source 120-2) to recipient 108.As shown in this example embodiment, tube 105-1 conveys fluid from fluidsource 120-1 to cassette 104. Tube 105-2 conveys fluid from fluid source120-2 to cassette 104. Note that fluid source 120-1 and fluid source120-2 can store the same or different fluids.

The controller 140 controls one or more components in cassette 104 todeliver fluid received from fluid source 120-1 and/or fluid source 120-2through tube 105-3 to recipient 108.

Control System:

By way of a non-limiting example, a mass flow based measurement systemtakes into account the ideal gas laws and mass conservation. Theequations hold for a closed system.

$\begin{matrix}{{M_{a\; 1} + M_{b\; 1}} = {M_{a\; 2} + M_{b\; 2}}} & \left( {{equation}\mspace{14mu} 1} \right) \\{{PV} = {\left. {M\;{RT}}\rightarrow M \right. = \frac{PV}{RT}}} & \left( {{equation}\mspace{14mu} 2} \right)\end{matrix}$R is a constant, so the equations factor down to:

$\begin{matrix}{{{\frac{P_{a\; 1}}{T_{a\; 1}}V_{a}} + {\frac{P_{b\; 1}}{T_{b\; 1}}V_{b}}} = {{\frac{P_{a\; 2}}{T_{a\; 2}}V_{a}} + {\frac{P_{b\; 2}}{T_{b\; 2}}V_{b}}}} & \left( {{equation}\mspace{14mu} 3} \right)\end{matrix}$

Estimation of temperatures as disclosed herein enables quickmeasurements and allows the device to operate without stopping the flowduring measurements by taking into account the full system states (suchas temperature), rather than assuming that they remain constant throughthe cycle.

More specifically, in one embodiment, an appropriate drive pressure canbe applied to a drive chamber side of a diaphragm pump to initiatedelivery of fluid in a fluid chamber side of the diaphragm pump to atarget recipient. Further embodiments herein can include discontinuingapplication of the pressure to the drive chamber at one or more timesduring a delivery cycle to perform a volume check to identify how muchof the fluid is present in the fluid chamber of the diaphragm pump overtime.

In one embodiment, the flow rate of fluid pumped to a target recipientequals the change in volume of the drive chamber over time.

During times of discontinuing application of the pressure to thediaphragm pump, embodiments herein can include taking into accountchanges in temperature of the gases (as a result of changing pressures)in one or more chambers when calculating the flow rate of delivering thefluid to the target recipient.

In one embodiment, a mass balance measurement is dependent on thetemperature of the working fluid. Given required measurement speed notedabove, the gas experiences adiabatic heating and cooling during themeasurement cycle. It may be difficult if not impossible to measure(with a temperature sensor) the gas temperature directly in the timeframe needed; therefore a thermal estimator is used to predict the gastemperature. In other words, the temperature of gases in one or morevolumes as discussed herein can change so quickly that a physicaltemperature sensor is unable to detect a respective change intemperature.

FIG. 4 is a hypothetical example diagram illustrating gas temperaturesin different resources during a delivery cycle. As described herein, oneor more temperatures can be estimated based on known system informationas discussed in more detail below.

In one embodiment, there are several additions to the ideal gas lawapproach that are used to achieve the required performancecharacteristics for a safe and reliable infusion pump. First there arecommon conditions when the flow rate is low and the outlet pressure islow such as when the pump is significantly higher than the patient. Inthis case, the required drive or pumping pressure is also very low. Verylow drive pressures are difficult to measure with common low costpressure transducers and it is very difficult to accurately control andmaintain low pressure in the positive tank. At higher flow rates orhigher outlet pressure, the drive pressures needed are much higher. Thiswide dynamic range makes it difficult to maintain pressure measurementresolution.

In order to: i) achieve all of the desired flow rate range given therelatively wide range of outlet pressure, ii) maximize pressuremeasurement resolution, and iii) maintain a driving pressure high enoughto avoid low pressure measurements near atmosphere, embodiments hereincan include a variable flow restriction that is added downstream of thepump chamber.

By way of a non-limiting example, this flow restriction can be avariable orifice. Given a desired set point flow rate, the variablefluid restriction opening is changed to maintain a minimum drivepressure. This variable fluid restriction further serves as a safetymechanism that can be positively shut or closed if desired.

Another requirement of infusion systems may be to maintain continuousflow. In one embodiment, the fluid delivery system as discussed hereindoes not stop the pumping during a flow rate measurement. Thus,embodiments herein can include providing a continuous or substantiallycontinuous flow of fluid delivery to a respective target recipient.

In order not to introduce measurement error, the volume measurementcycle can be performed extremely fast such as on the order ofmilliseconds. According to embodiments herein, a measurement cycle canbe less than 200 milliseconds. The fill cycle, such as filling thechamber of the diaphragm pump with fluid, also can be performed veryfast to minimize flow variation.

When the gases are moved at this high speed for all of the reasons abovethe isothermal Ideal Gas Law and Boyle's Law begin to breakdown.Specifically the assumption that the gas is isothermal is no longertrue. It is observed that the gas experiences adiabatic heating andcooling during the measurement cycle. As previously discussed,embodiments herein include estimating gas temperatures to compensate forthese errors.

In order to account for the temperature effects due to adiabatic heatingand cooling of the gas the pressure and volume relationships aretransformed as described above to yield:

$\begin{matrix}{V_{pc} = {V_{com}\frac{\left( {\frac{P_{{com}\; 2}}{T_{{com}\; 2}} - \frac{P_{{com}\; 1}}{T_{{com}\; 1}}} \right)}{\left( {\frac{P_{{pc}\; 1}}{T_{{pc}\; 1}} - \frac{P_{{pc}\; 2}}{T_{{pc}\; 2}}} \right)}}} & \left( {{equation}\mspace{14mu} 4} \right)\end{matrix}$

By way of a non-limiting example, the temperature can be estimated bytracking the system state variables at each time step of the controlloop. The physical parameters of the delivery system, such as volume,orifice size, and heat transfer coefficients combined with the measuredpressures allow the system to calculate an estimated temperature in eachof the gas volumes at any point during the pumping cycle using thefollowing energy balance equation:

$\begin{matrix}{\frac{\mathbb{d}T_{i}}{\mathbb{d}t} = {{\frac{1}{M_{i}C_{v}}\left\lbrack {{C_{p}{\sum\limits_{j}\;{T_{j}Q_{ji}}}} - {C_{p}T_{i}Q_{out}} - {C_{v}{T_{i}\left( {Q_{in} - Q_{out}} \right)}} + {H\left( {T_{wall} - T_{i}} \right)}} \right\rbrack} - {{\left( {\frac{C_{p}}{C_{v}} - 1} \right) \cdot \frac{T_{i}}{V_{i}}}\frac{\mathbb{d}V_{i}}{\mathbb{d}t}}}} & \left( {{equation}\mspace{14mu} 5} \right)\end{matrix}$

Where:

V=volume

Cv=specific heat at constant volume

Cp=specific heat at constant pressure

T=temperature

Q=mass flow

H=heat transfer coefficient

Event Detection:

In order to avoid medication and other fluids delivery errors, themeasurement and control systems typically must be able to quickly detectand in some cases automatically recover from a number of externaldisturbances. According to certain embodiments herein, the fluiddelivery system 100 can quickly detect the following conditions:

-   -   When the fluid delivery path becomes occluded or kinked,        peristaltic and mechanically actuated pumps continue trying to        deliver fluid until a pressure sensor measures that drive        pressure has exceeded a limit. This pressure is measured through        the wall of the flow path tubing, and therefore must be set to a        relatively high pressure. This can cause hazard to the patient        or the release of a bolus of fluid when the occlusion is        resolved. The fluid delivery system 100 as described herein can        be configured to operate at a low drive pressure and monitor        flow of liquid, rather than line pressure. As such, the system        can simply detect a stop of flow and indicate to the user that        an occlusion condition exists, without increasing drive pressure        to an unsafe level or charging the fluid line with high-pressure        liquid that can be released as a bolus.    -   An unexpected and sudden increase in the pressure from the        source fluid can occur at any time. This can be induced by a        patient or caregiver inadvertently squeezing or pressing on the        bag, forcing fluid into the patient. According to embodiments        herein, since the fluid delivery system 100 repeatedly and        constantly monitors pressure, this condition can be detected,        flow can be stopped, and an alarm can be activated.    -   Often medication is delivered in a small syringe by the        caregiver by injecting the medication into the IV line via a        Y-site or other access port. This small finite injection of        fluid is referred to as a Bolus or “IV push”. These actions are        often not delivered over the correct amount of time or they are        not recorded in the medical record in a timely manner. The fluid        delivery system 100 as described herein can be configured to        detect the pressure induced or the blockage of the line induced        by the action of the caregiver injecting fluid into the line via        a syringe.    -   The closed loop measurement and control system as employed by        fluid source 100 is able to sense the difference in viscosity of        the source fluid. Therefore it is able to discern the difference        between different types of fluid for example the difference        between blood, saline or saline mixed with Dextrose. According        to yet further embodiments, the fluid delivery system 100 can be        configured to differentiate between air in the source line or        fluid in the source line. This ability to detect air can be used        to more accurately calculate the total volume of fluid infused        as well as enable a number of workflow advantages such as        automatic detection of an empty source container and notifying        the user appropriately.        Dose Correction:

A very common problem encountered during the administration of smalldoses of medication is that errors are induced due to the unknown volumeof the tubing connecting the medication source and the patient. In somecases the contained volume of the tubing and administration set can bemany times larger than the dose of the mediation delivered. Today,caregivers must either manually flush the line, pushing the dose throughthe tubing to the patient. Extra medication is provided by the pharmacysuch that the correct dose can be delivered to the patient and themedication left in the volume of the tubing is thrown away or theincorrect dose is administered. Because the fluid delivery system 100 isclosed loop and measures the volume of fluid being transferred directlyand the contained volume of the administration set is known, the correctdose is delivered to the patient consistently. Furthermore, the currentembodiment of the administration set (such as cassette and tubing)accommodates two inputs. One input can be used for the medicationdelivery via a syringe and the second input can be used to flush theline and push the dose through the tubing.

Secondary Administration Automation:

Most medications such as antibiotics are administered in combinationwith a primary fluid such as normal saline. This secondary or“piggyback” administration today requires that the caregiver positionthe secondary fluid container at a specific height relative to theprimary. This method relies on gravity to function properly. Like the IVpush or Bolus delivery, this is not recorded by the device thusrequiring the caregiver to document the fluid delivery properly. Theclosed loop control and direct volumetric fluid measurement combinedwith a dual input administration set enables the complete automation ofsecondary fluid administration. According to certain embodiments herein,the fluid delivery system 100 is able to:

-   -   Deliver from syringe, or bag on secondary—intermittent or        complete    -   Automatically switch between the primary fluid source 120-1 and        secondary fluid source 120-2    -   Scheduled (i.e. time delay or intermittent) secondary    -   Deliver the secondary fluid without regard to the relative        positions of the fluid sources, pump or patient    -   Correctly and accurately deliver, measure and record all fluid        delivery events

MORE DETAILED DESCRIPTION OF EMBODIMENTS

In one non-limiting example embodiment, the fluid pumping system asdescribed herein is centered around a pumping chamber(“IPC”—Intermediate Pumping Chamber) that consists of a volumebifurcated by a flexible diaphragm. One side of the IPC is connected tothe pneumatic portion of the fluidic system. The other side of the IPCis connected to the hydraulic portion of the fluidic system. Hydraulicpumping is achieved by applying alternating positive and negativepressure to the pneumatic side of the IPC, thus moving the diaphragmback and forth (or in and out).

FIG. 2 is a more specific example diagram illustrating componentsdisposed in a fluid delivery system and corresponding disposablecassette according to embodiments herein.

As previously discussed, the controller 140 of the fluid delivery system100 controls operation of diaphragm pumps 130 and 131 in disposablecassette 104 to precisely deliver fluid from one or more fluid sourcessuch as fluid source 120-1 and fluid source 120-2 to a respectiverecipient 108.

In one embodiment, the flow of liquid through the system is controlledby adjustments to the drive pressure from the Positive Tank 170-1 and avariable hydraulic resistor (component such as fluid resistor 115) thatis controlled by a motor or other suitable resource. Flow rate ismeasured using periodic volume calculations described below, and thecontrol parameters are adjusted accordingly to drive the error betweenmeasured flow rate and target flow rate to zero.

Pump Cycle Overview

In accordance with yet further embodiments, a pump cycle is defined as amotion of drawing fluid into a diaphragm pump and then applying pressureto the diaphragm pump to deliver the fluid to a recipient. In accordancewith a specific non-limiting example embodiment, a pump cycle can bedefined as at least partially moving of the membrane 127 in thediaphragm pump 130 from one extreme (such as “full”) to another extreme(such as “empty”).

As shown in FIG. 2 and more specific FIG. 3, membrane 127 divides thediaphragm pump 130 to include chamber 130-1 and chamber 130-2. Membrane127 prevents fluid in chamber 130-1 from passing to chamber 130-2, andvice versa.

The membrane 127 dividing diaphragm pump 130 into chamber 130-1 andchamber 130-2 is flexible. When a negative pressure is applied tochamber 130-2, the volume of chamber 130-1 expands and draws fluid fromfluid source 120-1 into chamber 130-1.

Conversely, when a positive pressure is applied to chamber 130-2, thevolume of chamber 130-1 decreases expelling fluid from chamber 130-1downstream to a respective recipient 108.

The total volume or capacity of chamber 130-1 and chamber 130-2 issubstantially constant regardless of the position of the membrane 127.Based on knowing the volume of fluid in chamber 130-2, one is able todetermine a corresponding volume of chamber 130-1. For example, if thetotal volume of the diaphragm pump 130 is Vtotal, and the volume ofchamber 130-2 is V2, the fluid delivery system 100 can determine thevolume of chamber 130-1 by subtracting V2 from Vtotal.

Diaphragm pump 131 operates in a similar manner as diaphragm pump 130.Membrane 128 divides the diaphragm pump 131 to include chamber 131-1 andchamber 131-2. Membrane 128 prevents fluid in chamber 131-1 from passingto chamber 131-2, and vice versa.

The membrane 128 dividing diaphragm pump 131 into chamber 131-1 andchamber 131-2 is flexible. When a negative pressure is applied tochamber 131-2, the chamber 131-1 draws fluid from fluid source 120-2into chamber 131-1. Conversely, when a positive pressure is applied tochamber 131-2, the diaphragm pump 131 expels fluid from chamber 131-1downstream to a respective recipient 108.

In a similar manner as previously discussed for diaphragm pump 130, thetotal volume or capacity of chamber 131-1 and chamber 131-2 issubstantially constant regardless of the position of the membrane 128.Based on knowing the volume of fluid in chamber 131-2, the controller140 is able to determine a corresponding volume of chamber 131-1. Forexample, if the total volume of the diaphragm pump 131 is Vtotal, andthe volume of chamber 131-2 is determined as being V2, the fluiddelivery system 100 can determine the volume of chamber 131-1 bysubtracting V2 from Vtotal.

In this example embodiment, as shown in FIG. 2, temperature sensor 152measures a temperature (e.g., TTC) of gas in chamber 150 (common tank)and provides a baseline from which to estimate the temperatures of gasesin one or more of the following resources: chamber 150, pump chamber130-2, positive tank 170-1, negative tank 170-2, etc.

As further discussed below, estimation of the temperature enables a moreaccurate assessment of how much of fluid in pump chamber 130-1 has beenpumped in a direction towards the target recipient 108 over conduit path138 (such as a path from diaphragm pump 130 through a combination ofcheck valve 125-2, filter 112, fluid resistor 115, gas detectionresource 110, and tube 105-3 to recipient 108).

Initially, to fill the chamber 130-1 with fluid from fluid source 120-1,the controller 140 of fluid delivery system 100 applies a negativepressure or vacuum to chamber 130-2. At such time, pump chamber 130-2reduces in volume, causing the chamber 130-1 to fill with fluid receivedfrom fluid source 120-1 through check valve 125-1. Check valve 125-1prevents fluid from flowing in a backward direction from diaphragm pump130 to fluid source 120-1. Check valve 125-2 prevents fluid from flowingin a backward direction from conduit path 138 to the pump chamber 130-1.

Assume that prior to filling, the chamber 130-1 is substantially emptyof fluid. In one embodiment, to draw fluid into chamber 130-1 withnegative pressure from tank 170-2 as discussed above, the controller140-1 generates respective control signals V1 and V5 to open valve 160-1and 160-5 (while all other valves are closed) to draw fluid from fluidsource 120-1 and check valve 125-1 into chamber 130-1.

Subsequent to chamber 130-1 being filled with fluid, the controller 140controls settings of the valves 160 to apply a positive pressure fromtank 170-1 to chamber 130-2 of diaphragm pump 130. For example, viageneration of control signals V4 and V5, the controller 140 opens valves160-4 and 160-5 and closes all other valves. The flow of gas frompositive tank 170-1 to pump chamber 130-2 causes pumping of fluid fromchamber 130-1 through check valve 125-2 along conduit path 138 to thetarget recipient 108. As previously discussed, during application ofpositive pressure o chamber 130-2, check valve 125-1 prevents fluid inchamber 130-1 from flowing back into fluid source 120-1.

As shown, the conduit path 138 through cassette 104 can include filterresource 112 that eliminates air and/or particulate matter in the fluidfrom being pumped to the target recipient 108.

Additionally conduit path 138 can include an in-line flow resistor 115.In one embodiment, the controller 140 utilizes the in-line flow resistoras one means to control a rate of delivering fluid to the targetrecipient 108. For example, at a given driving pressure in chamber130-2, to decrease a rate of flow, the controller 140 increases aresistance of the in-line flow resistor 115. To increase a flow rate offluid from the chamber 130-1 to the target recipient 108, the controller140 decreases a resistance of the in-line flow resistor 115.

Note that drive pressure in chamber 130-2 is another way to control arate of delivering fluid to the target recipient 108. At a givenposition of an in-line flow resistor 115, the controller can use airpump 180 and pressure gauge 135-4 to set a target drive pressure inpositive tank 170-1. That drive pressure can then be applied to pumpchamber 130-2 (by opening valve 160-5) to drive the fluid in chamber130-1 to target recipient 108. To increase a flow rate of fluid from thechamber 130-1 to the target recipient 108, the controller 140 can beconfigured to increase the drive pressure in positive tank 170-1. Todecrease a flow rate the controller 140 can be configured to decreasethe drive pressure in positive tank 170-1.

Note that conduit path 138 also can include gas detector resource 110.The gas detector resource 110 can be configured to detect presence ofair (or other gases) in the fluid being pumped through conduit path 138to the target recipient 108. Based on feedback from the gas detectorresource 110 as monitored by the controller 140, the controller 140 canbe configured to sound an alarm in the event of detecting presence ofgas in the fluid pumped to the target recipient 108.

During a delivery phase, the controller 140 can be configured to mainlyapply pressure to chamber 130-2 with gas from tank 170-1 or tank 150 tocause the fluid in chamber 130-1 to be pumped to the target recipient108. Delivery of the fluid in chamber 130-1 through conduit path 138 totarget recipient 108 can be controlled by the controller 140 inaccordance with a pre-selected fluid delivery rate. In other words, thecontroller 140 controls positive pressure applied chamber 130-1 tocontrol a respective fluid flow rate. As further discussed below,embodiments herein can include at least temporarily discontinuingapplication of pressure to chamber 130-2 in order to perform ameasurement of fluid remaining in chamber 130-1. As shown and discussed,discontinuing application of pressure to chamber 130-2 can at leasttemporarily reducing a pressure in chamber 130-2.

During a fluid delivery phase, the controller 140 supplies asubstantially constant pressure to the chamber 130-2. Because themembrane 127 is flexible, the pressure in chamber 130-2 exerts a forceon the fluid in chamber 130-1. In general, via application of theappropriate pressure to chamber 130-2, the controller 140 is able tofairly accurately pump the fluid at a desired flow rate. However, incertain situations, the delivery system 100 can be perturbed, resultingin errors in the flow rate. For example, as previously mentioned, thefluid source 120-1 may be squeezed, the elevation of fluid source 120-1may change, etc. Any of these conditions can impact an accuracy of adesired fluid delivery rate.

Note that in addition to applying positive pressure to the pump chamber130-2 during a fluid delivery phase, embodiments herein can includeoccasionally checking how much of the fluid drawn into the chamber 130-1has been pumped towards the target recipient 108 through conduit path138. This enables the controller 140 to accurately determine the actualflow rate of fluid, even during times when the system conditions areperturbed.

More specifically, one way to measure a fluid delivery rate during arespective delivery phase is to repeatedly measure how much of the fluidin the chamber 130-1 has been pumped towards target recipient 108 onconduit path 138 at one or more MEASUREMENT times during the deliveryphase. For example, the controller 140 the controller can initiatechecking the volume of gas in chamber 130-2 over multiple sample timesof a positive pressure delivery cycle. Because it is known how much gasis initially in the chamber 130-2 at the beginning of a delivery phase,and based on calculating how much gas is in chamber 130-2 at differenttimes, etc., the controller is able to accurately measure a rate ofpumping or delivering the fluid from fluid source 120-1 over conduitpath 138 to the target recipient 108 in between times of filling thechamber 130-2. Thus, the controller 140 is able to accurately measurefluid delivery in very small increments of time between successivecycles of refilling the chamber 130-1 with additional fluid.

In one embodiment, as previously discussed, the total volume of thediaphragm pump 120-1 including chamber 130-1, chamber 130-2 and conduitthere between is a known quantity. One embodiment herein includescalculating how much fluid remains in chamber 130-1 based on knowing thevolume of chamber 130-2. That is, the volume of the chamber 130-1 can becalculated by subtracting the volume of chamber 130-1 from the totalvolume of diaphragm pump 130. As discussed below, the volume of chamber130-2 is initially an unknown quantity but is calculated based onpressure and estimated temperature.

FIG. 5A is an example diagram illustrating fluid measurements duringfluid delivery according to embodiments herein. As shown, graph 510-1illustrates application of pressure for more than 95% of a deliverycycle. PC represents the pressure of gas in chamber 130-2; COMrepresents the pressure of gas in the chamber 150.

In between times of applying pressure to chamber 130-2 (such as timeslabeled as FLUID DELIVERY), the controller 140 of fluid delivery system100 periodically or occasionally, at multiple times, performs ameasurement (labeled as MEASUREMENT) to determine a volume of chamber130-2 of diaphragm pump 130. By way of non-limiting example embodiment,the controller 140 initiates applying an approximately constant pressureduring FLUID DELIVERY portions of a fluid delivery cycle while theapplied pressure to chamber 130-2 is reduced briefly during eachrespective MEASUREMENT.

In this example embodiment, graph 520-1 illustrates changes intemperature of respective gases that occur during each of themeasurements. For example, Tcom represents the estimated temperature ofthe gas in the chamber 150; Tpc represents the temperature of gas in thechamber 130-2.

In general, in one non-limiting example embodiment, the duty cycle ofperforming measurements versus delivering fluid is relatively small.That is, in one non-limiting example embodiment, most of a fluiddelivery cycle (delivery phase) can be used to deliver correspondingfluid in chamber 130-1 of pump 130 to recipient 108. For a small portionof the delivery cycle, the controller 140 operates respective resourcesto perform a corresponding volume MEASUREMENT of the chamber 130-2 asshown. Recall that after a volume of the chamber 130-2 is known, thevolume of chamber 130-1 can easily be determined.

FIG. 5B is an example diagram illustrating more particular details of afluid delivery cycle according to embodiments herein.

Graph 510-2 shows the pressures measured in the system during a fluiddelivery cycle. Graph 520-2 shows the estimated temperatures measured inthe system during a fluid delivery cycle.

For the discussion here, the focus will be on pumping from the lefthydraulic channel (e.g., from fluid source 120-1, through check valve125-1, to diaphragm pump 130, through conduit path 138 to the targetrecipient 108), but the same patterns, behaviors and measurements applyto the right channel (e.g., from fluid source 120-2, through check valve125-2, to diaphragm pump 131, to the target recipient 108) as well.

As previously discussed, one or more diaphragm pumps can be operated inany suitable manner to deliver one or more fluids to a target recipient108. For example, the controller 140 can individually and accuratelycontrol the flow rate of each of the fluids delivered to the targetrecipient 108.

In one non-limiting example embodiment, the controller 140 can pump afirst fluid from fluid source 120-1 to the target recipient 108 at afirst fluid delivery rate; the controller 140 can pump a second fluidfrom fluid source 120-2 to the target recipient 108 at a second fluiddelivery rate, the first delivery rate can be different than the seconddelivery rate.

At or around time [A] in FIG. 5B, a delivery cycle begins by resettingthe pressures in the positive tank 170-1 and negative tank 170-2. Thecontroller 140 sets the solenoid valves 165-1, 165-2, 165-3, 165-4, and165-5 (via generation of control signals V1, V2, V3, V4, and V5) to aclosed position. The controller 140 activates (turns ON) air pump 180 tobring the tanks to the desired drive pressure.

At time [B], valves 160-1 (V1) and 160-5 (V5) are opened to apply thepressure in the negative tank 170-2 to the chamber 130-2. The negativepressure draws the diaphragm membrane 127 back towards tank 150, fillingchamber 130-1 with fluid from fluid source 120-1. Check valve 125-1(CV1) opens due to the differential pressure. Fluid such as liquid fromfluid source 120-1 is drawn into the chamber 130-1 of the diaphragm pump130.

At time [C] valves 160-4 (via generation of signal V4) and 160-5 (viageneration of signal V5) are opened to apply the pressure in thepositive tank 170-1 to the chamber 130-2 of the diaphragm pump 130. Thepositive pressure causes check valve 125-1 (CV1) to close and checkvalve 125-2 (CV2) to open. This causes the liquid in the chamber 130-2of the diaphragm pump 130 to flow on conduit path 138 towards the targetrecipient 108 such as a patient.

In one embodiment, some time after the chamber 130-2 of diaphragm pump130 is brought to positive pressure, the controller 140 performs volumecalculations such as at times [D], [E], [F], etc. Aspects of the volumecalculation are discussed in more detail below. As previously discussed,one or more volume calculations can be performed periodically during thetime that the chamber 130-1 is emptying (e.g., during times [C] through[I]).

After the last volume measurement at time [I], or at any time during thedelivery phase, the controller 140 calculates a flow rate from thevolume measurements. Based on the calculated flow rate the controller140 can determine if adjustments are needed to one or both of the twoflow control parameters: target drive pressure in positive tank 170-1,in-line fluid resistance 115.

In general, increasing the pressure of gas in the chamber 130-2 of thediaphragm pump 130 increases the rate of fluid delivery; decreasing amagnitude of gas pressure applied to chamber 130-2 decreases arespective rate of fluid delivery.

Additionally, increasing an amount of fluid resistance provided by fluidresistor 115 reduces a rate at which the fluid in chamber 130-1 isdelivered to the recipient 108; decreasing amount of fluid resistanceprovided by fluid resistor 115 increases a rate at which the fluidchamber 130-1 is delivered to the recipient 108.

The fluid delivery cycle restarts when the air pump 180 is turned on attime [J] to reset the pressures in the positive tank 170-1 and negativetank 170-2 again.

Measure Cycle Overview

FIG. 6 is an example diagram illustrating a MEASUREMENT (time E) duringa fluid delivery cycle according to embodiments herein.

Graph 610 illustrates gas pressures in each of multiple volumes. In thisexample embodiment, the pressure signal labeled PC in graph 610represents the pressure of a gas in chamber 130-2 as measured bypressure sensor 135-5 (which produces pressure signal P5). The pressuresignal labeled COM in graph 610 represents the pressure of a gas inchamber 150 as measured by pressure sensor 135-3 (which producespressure signal P3).

Graph 620 illustrates estimated temperatures of the respective gases inthe chamber 150 and chamber 130-2.

At the start of a respective fluid delivery cycle, the chamber 150(Common Tank), positive tank 170-1, and the diaphragm pump 130 (e.g.,Left IPC) are all at to the same pressure such as the driving pressureof the system. The driving pressure represents the pressure of the gasapplied to chamber 130-2 prior to time T1.

At point [1] in graph 610, the controller 140 generates control signalsV1, V2, V3, etc., to close all of the valves 160 to isolate the gasvolumes. The controller controls valve 160-3 (via signal V3) to an openstate to vent the chamber 150 (Common Tank) to ambient pressure.

When the pressure in the chamber 150 reaches ambient pressure atapproximately point [2], the controller 140 controls valve 160-3 (viageneration of signal V3) to a closed position again such that all of thegas volumes are again isolated.

After a brief stabilization period (such as approx. 50 milliseconds), atapproximately time, T1, (shown as points [3] and [4]), the controller140 controls valve 160-5 (via generation of signal V5) to an open stateto merge the gas in chamber 130-2 with the gas in chamber 150. The gaspressure in the chamber 130-2 and tank 150 equalize at or around point[5] in graph 610. In one embodiment, the volume of chamber 130-2 andchamber 150 are approximately the same. In this example embodiment,opening of valve 160-5 causes the pressure in the chamber 130-2 toreduce by approximately 50%. The amount of reduction in pressure appliedto chamber 130-2 varies depending on a volume of chamber 130-2 and avolume of chamber 150.

After another brief stabilization period (such as approx. 50milliseconds or at point [6]), the controller 140 controls valve 160-4(via generation of signal V4) to an open state to connect the chamber130-2 (Left IPC) and the chamber 150 to the positive tank 170-1 to bringall three gas volumes up to the driving pressure again, during which thepressure in the chamber 130-2 causes the chamber 130-1 to pumprespective fluid to the target recipient 108. Thus, embodiments hereininclude at least temporarily discontinuing application of the drivepressure in order to obtain pressure measurements at different times.

In one embodiment, the actual volume calculation produced by thecontroller 140 occurs based on measurements of pressure collected by thecontroller 140 at or around points [3], [4], and [5].

At substantially time T1 or point [3], the controller 140 receivessignal P5 generated by pressure sensor 135-5 to determine the pressurePpc of the gas applied to chamber 130-2.

At substantially time T1 or point [4], the controller 140 receivessignal P3 generated by pressure sensor 135-3 to determine the pressurePcom of the gas in chamber 150.

At substantially time T2 or point [5], the controller 140 receivessignal P3 or P5 generated by pressure sensor 135-3 or pressure sensor135-5 to determine the pressure Pmerge of the gas in chamber 150.

According to one embodiment, the controller 140 determines the volume ofgas in chamber 130-2 using isothermal ideal gas laws as follows:P ₁ V ₁ =P ₂ V ₂  (equation 6)

-   -   For:    -   V_(pc)=Unknown volume of the chamber 130-2 of diaphragm pump 130        (left IPC)    -   V_(com)=the known volume of the chamber 150 (Common Tank)    -   P_(pc)=pressure of the chamber 130-2 Left IPC at point [4]    -   P_(com)=pressure of the chamber 150 (Common Tank) at point [3]    -   P_(merge)=P_(pc)=P_(com) pressure when the two chambers (130-2        and 150) are equalized at point [5]

$\begin{matrix}{{{{V_{pc}P_{pc}} + {V_{com}P_{com}}} = {{V_{pc}P_{merge}} + {V_{com}P_{merge}}}}\vdots} & \left( {{equation}\mspace{14mu} 7} \right) \\{V_{pc} = {V_{com}\frac{P_{merge} - P_{com}}{P_{pc} - P_{merge}}}} & \left( {{equation}\mspace{14mu} 8} \right)\end{matrix}$

An isothermal calculation assumes that all transient thermal effects inthe system have had time to dissipate. This dissipation can take on theorder of seconds to occur, depending on the details of the system. Ifthe volume calculation is performed prior to the system returning tothermal equilibrium, the residual temperature differences will introduceerrors in the volume calculation, which will in turn cause errors in theresultant flow rate calculation.

In accordance with one embodiment, in order to achieve the range of flowrates required in an infusion pump system, and to minimize errors due tovolume changes during the measurement cycle, the current embodiment canbe configured to calculate a volume of fluid pumped to the targetrecipient 108 before the transient thermal effects have dissipated. Inorder to maintain volume calculation accuracy, embodiments herein takeinto account thermal effects to produce a more accurate fluid deliveryrate.

In one embodiment, the temperature changes in the gas happen too fast tobe measured by standard thermal sensors. In other words, thermal sensorsmay not be able to accurately measure fast changing temperatures of thegases in tank 150, chamber 130-2, etc., during a respective pressurechanges shown in graph 600. To address this issue, one embodiment hereinincludes estimating temperatures of the volumes of interest to calculatean actual fluid delivery rate. As mentioned, the temperature sensor 152measures an average temperature of gas in the common tank 150. However,due to its thermal mass, the temperature sensor 152 may not be able toaccurately reflect an actual temperature of gas in chamber 150.

There are a number of parameters that affect the temperature of thegases in the different volumes (e.g., tank 150, chamber 130-2, etc.)over time. For example, thermal changes come primarily from 3 sources inthe pneumatic system:

1. Adiabatic heating or cooling due to pressure changes in the chamber

2. Heat transfer between the gas and the chamber wall

3. Volume change due to flow rate out of the IPC chamber

One embodiment herein includes modeling the fluid delivery system 100 toaccurately estimate the temperature of the chambers of interest. Forexample, as mentioned, the change in pressure of chambers (such as pumpchamber 130-2 and chamber 150) as shown and discussed with respect toFIG. 6 causes the temperature of the pump chamber 130-2 and the commontank 150 to vary. More specifically, between point 1 and point 2 in FIG.6, the pressure of the common tank 150 drops significantly, causing thetemperature of the gas, Tcom, in chamber 150 (common tank) to drop. Aspreviously discussed, the pressure of gas in the respective chambers(e.g., P5, P3, etc.) is continuously and accurately measured usingrespective pressure sensors 135-5, 135-3, etc.

In one embodiment, a first model is used to estimate temperature changesin the chambers due to adiabatic heating and/or cooling. In other words,any suitable equations can be used to determine a change in thetemperature of the gases in the chambers as a result of the pressureschanging. Increasing a pressure of a gas causes an increase intemperature; decreasing a pressure of a gas causes a decrease intemperature.

Another parameter affecting the temperature of the gases in the chambersis the thermal characteristics of the chambers themselves and conduitsin between. The dark lines in FIG. 2 represent conduits interconnectingthe different components in fluid delivery system 100. For example, thedark line extending between diaphragm pump 130 and valve 160-5represents a conduit; the dark line between valve 160-5 in chamber 150represents a conduit; and so on. Via respective conduits, each of thecomponents (such as check valve 125-1, diaphragm pump 130, valve 160-5,etc.) in fluid delivery system 100 are interconnected.

According to embodiments herein, the thermal properties of the chambers(e.g., common tank 150, pump chamber 130-2, etc.) can be characterizedand modeled to identify how quickly they sink or source heat when thereis a change in temperature caused by a change in pressure. As anexample, and as discussed, the reduction in the pressure of a tank cancause the temperature of the gas in the tank to decrease. Thetemperature of the tank itself may be higher in magnitude than thetemperature of the gas, resulting in a flow of heat from the tank orchamber to the gas therein. Thermal flow causes the temperature of thegas in the chamber to eventually become the substantially the same asthe temperature in the respective tank over time. Conversely, anincrease in pressure of the tank can cause the temperature to increase.The flow of heat from gas to the tank or chamber decreases thetemperature of the gas.

One embodiment herein includes estimating the temperature of the gas andtaking into account thermal heat flow using a respective thermal model.The thermal model takes into account the transfer of heat from the gasto the respective chamber or tank and/or a transfer of heat from therespective chamber or tank to the gas. The heat transfer will likelyvary depending on the type of material used to fabricate the tanks andrespective interconnections. Certain material such as metal will be morethermally conductive; material such as plastic will be less thermallyconductive.

As discussed above, the changes in the temperature of the gases due tochanges in pressure are deterministic and thus can be accuratelyestimated. However, the flow of energy from tank to gas or from gas totank will impact the temperature. Embodiments herein include producing amore accurate estimate of temperature by taking into account these flowsof energy at different times based on thermal modeling.

Another factor affecting the temperatures of the gases in the chambersis the volume of the pump chamber 130-2 and how quickly it changes overtime due to pumping of the fluid in the diaphragm pump chamber to thetarget recipient. For example, if the fluid in the pump chamber 130-2 ispumped at a very slow rate to target recipient 108, then volume changeeffects are minor or potentially negligible. Conversely, if the fluid inpump chamber 130-1 is pumped at a relatively high rate to the targetrecipient 108, then the volume change effects become more significant.As discussed herein, embodiments herein take into account the volumechanges.

In one embodiment, the controller 140 generates the estimation oftemperatures at discrete points in time such as between one second andone nanosecond. For each time step (i.e., each discrete time ofproducing an estimation of temperature) of the control system, thechange in temperature due to those three sources is calculated for eachpneumatic volume using the measured pressure as an input. The components(e.g., adiabatic effects, heat transfer effects, volume change effects)can be measured individually and/or in combination to produce arespective estimated temperature.

In the following equations subscripts ‘i’ and T are used to denote eachof the pneumatic volumes 130-2, 150, 170-1, 170-2. The subscript ‘i’represents the chamber for which the temperature is being estimated; thesubscript ‘j’ represents the associated chamber. For example, whenestimating a temperature for the pump chamber 130-2, the subscript ‘i’represents the pump chamber 130-2; subscript ‘j’ represents the commontank 150. When estimating a temperature for the common tank 150, thesubscript ‘i’ represents the common tank 150; subscript ‘j’ representsthe pump chamber 130-2, and so on.

By way of a non-limiting example, the temperature at time (n+1) is thencalculated based on that change rate:

$\begin{matrix}{\frac{\mathbb{d}T_{n}}{\mathbb{d}t} = {\left( {{Heat}\mspace{14mu}{Transfer}\mspace{14mu}{Effects}} \right) + \left( {{Pressure}\mspace{14mu}{Change}\mspace{14mu}{Effects}} \right) + \left( {{Volume}\mspace{14mu}{Change}\mspace{14mu}{Effects}} \right)}} & \left( {{equation}\mspace{14mu} 9} \right) \\{T_{n + 1} = {T_{n} + {{\mathbb{d}t}\frac{\mathbb{d}T_{n}}{\mathbb{d}t}}}} & \left( {{equation}\mspace{14mu} 10} \right)\end{matrix}$

Heat transfer effects are based on the temperature of the gas in thechamber, the temperature of the chamber wall, and the heat transfercoefficient between the two. For example, in one embodiment:Heat Transfer Effects H(T _(wall) −T _(i))  (equation 11)

-   -   T_(i)=last estimation of temperature for chamber i    -   H=heat transfer coefficient    -   T_(wall)=ambient temperature T_(tc) as sensed by temperature        sensor 152    -   Pressure change effects are based on the mass flow from once        chamber to another due to pressure differential between the two        chambers:

$\begin{matrix}{\mspace{79mu}{Q_{ij} = {C_{ij}A_{ij}\sqrt{2{\rho_{i}\left( {P_{i} - P_{j}} \right)}}}}} & \left( {{equation}\mspace{11mu} 12} \right) \\{\mspace{79mu}{{Q_{in} = {\sum\limits_{j}\; Q_{ji}}}\mspace{79mu}{Q_{out} = {\sum\limits_{j}\; Q_{ij}}}}} & \left( {{equations}\mspace{14mu} 13\mspace{14mu}{and}\mspace{14mu} 14} \right) \\{{{Pressure}\mspace{14mu}{Change}\mspace{14mu}{Effects}} = {\frac{1}{M_{i}C_{v}}{\quad\left\lbrack {{C_{p}{\sum\limits_{j}\;{T_{j}Q_{ji}}}} - {C_{p}T_{i}Q_{out}} - {C_{v}{T_{i}\left( {Q_{in} - Q_{out}} \right)}}} \right\rbrack}}} & \left( {{equation}\mspace{14mu} 15} \right)\end{matrix}$

-   -   Where:    -   M_(i)=mass of gas in chamber i;    -   Q_(ij) is the mass flow rate from chamber i to chamber j.    -   C_(ij) is the discharge coefficient of the valve between chamber        i and j    -   A_(ij) is the area of the orifice of the valve between chamber i        and j    -   ρ_(i) is the density of the gas in chamber i

Volume change effects are based on any changes in actual volume of thechamber in question. In one embodiment, this effect only applies tochamber 130-2, which can change size due to motion of membrane 127.

$\begin{matrix}{{{Volume}\mspace{14mu}{Change}\mspace{14mu}{Effects}} = {{\left( {\frac{C_{p}}{C_{v}} - 1} \right) \cdot \frac{T_{i}}{V_{i}}}\frac{\mathbb{d}V_{i}}{\mathbb{d}t}}} & \left( {{equation}\mspace{14mu} 16} \right)\end{matrix}$

-   -   Where:    -   V=volume    -   Cv=specific heat at constant volume    -   Cp=specific heat at constant pressure

The estimated temperature curves through the pumping and measurementcycles can be seen in FIGS. 5a, 5b , and 6.

In this method the control system has an estimated temperature for eachgas chamber that can be used in a modified ideal gas law volumecalculation that takes temperature into account:

$\begin{matrix}{V_{pc} = {V_{com}\frac{\left( {\frac{P_{{com}\; 2}}{T_{{com}\; 2}} - \frac{P_{{com}\; 1}}{T_{{com}\; 1}}} \right)}{\left( {\frac{P_{{pc}\; 1}}{T_{{pc}\; 1}} - \frac{P_{{pc}\; 2}}{T_{{pc}\; 2}}} \right)}}} & \left( {{equation}\mspace{14mu} 17} \right)\end{matrix}$

-   -   Where:    -   V_(pc)=Unknown volume of the chamber 130-2 of diaphragm pump 130        (e.g., Left IPC)    -   V_(com)=the known volume of the chamber 150    -   P_(com1)=pressure P₃ from pressure sensor 135-3 of the chamber        150 at point [3]    -   P_(com2)=pressure P₃ from pressure sensor 135-3 of the chamber        150 at point [5]    -   P_(pc1)=pressure P₅ from pressure sensor 135-5 of the chamber        130-2 at point [4]    -   P_(pc2)=pressure P₅ from pressure sensor 135-5 of the chamber        130-2 at point [5]    -   T_(com1)=estimated temperature of the chamber 150 at point [3A]    -   T_(com2)=estimated temperature of the chamber 150 at point [5A1]    -   T_(pc1)=estimated temperature of the chamber 130-2 at point [4A]    -   T_(pc2)=estimated temperature of the chamber 130-2 at point        [5A2]

As previously discussed, the volume of the chamber 130-1 can becalculated by subtracting the calculated VPC (e.g., volume of thepumping chamber 130-2) from the total volume of the diaphragm pump 130.The total volume of the diaphragm pump 130 is equal to the volume ofchamber 130-1 plus the volume of chamber 130-2 and is a known quantity.

In a further embodiment, the volume of chamber 130-1 is not calculated,and flow rate is calculated by simply taking the difference in volumebetween subsequent calculations of the volume of chamber 130-2. In otherwords, the change in volume of pump chamber 130-2 over time isindicative of a pumping flow rate and can be used as a basis tocalculate the flow rate. The controller 140 can be configured toprecisely determine a respective flow rate of delivering fluid fromchamber 130—one of diaphragm pump 130 based on the multiple measurementstaken at times C, D, E, etc., in FIG. 5b . The flow rate=(change involume of fluid in chamber 130-1)/(range of delivery time).

Using a temperature-corrected volume calculation (based on estimation ofgas temperatures as described herein) allows the system to have ameasure sequence that happens on the order of 80 milliseconds, ratherthan on the order of seconds while maintaining calculation accuracy.

FIG. 7 is an example block diagram of a computer device for implementingany of the operations as discussed herein according to embodimentsherein.

In one embodiment, fluid delivery system 100 includes a computer system750 to execute controller 140.

As shown, computer system 750 of the present example includes aninterconnect 711, a processor 713 (such as one or more processordevices, computer processor hardware, etc.), computer readable storagemedium 712 (such as hardware storage to store data), I/O interface 714,and communications interface 717.

Interconnect 711 provides connectivity amongst processor 713, computerreadable storage media 712, I/O interface 714, and communicationinterface 717.

I/O interface 714 provides connectivity to a repository 780 and, ifpresent, other devices such as a playback device, display screen, inputresource 792, a computer mouse, etc.

Computer readable storage medium 712 (such as a non-transitory hardwaremedium) can be any hardware storage resource or device such as memory,optical storage, hard drive, rotating disk, etc. In one embodiment, thecomputer readable storage medium 712 stores instructions executed byprocessor 713.

Communications interface 717 enables the computer system 750 andprocessor 713 to communicate over a resource such as network 190 toretrieve information from remote sources and communicate with othercomputers. I/O interface 714 enables processor 713 to retrieve storedinformation from repository 780.

As shown, computer readable storage media 712 is encoded with controllerapplication 140-1 (e.g., software, firmware, etc.) executed by processor713. Controller application 140-1 can be configured to includeinstructions to implement any of the operations as discussed herein.

During operation of one embodiment, processor 713 (e.g., computerprocessor hardware) accesses computer readable storage media 712 via theuse of interconnect 711 in order to launch, run, execute, interpret orotherwise perform the instructions in controller application 140-1stored on computer readable storage medium 712.

Execution of the controller application 140-1 produces processingfunctionality such as controller process 140-2 in processor 713. Inother words, the controller process 140-2 associated with processor 713represents one or more aspects of executing controller application 140-1within or upon the processor 713 in the computer system 750.

Those skilled in the art will understand that the computer system 750can include other processes and/or software and hardware components,such as an operating system that controls allocation and use of hardwareresources to execute controller application 140-1.

In accordance with different embodiments, note that computer system maybe any of various types of devices, including, but not limited to, awireless access point, a mobile computer, a personal computer system, awireless device, base station, phone device, desktop computer, laptop,notebook, netbook computer, mainframe computer system, handheldcomputer, workstation, network computer, application server, storagedevice, a consumer electronics device such as a camera, camcorder, settop box, mobile device, video game console, handheld video game device,a peripheral device such as a switch, modem, router, or in general anytype of computing or electronic device. In one non-limiting exampleembodiment, the computer system 850 resides in fluid delivery system100. However, note that computer system 850 may reside at any locationor can be included in any suitable resource in network environment 100to implement functionality as discussed herein.

Functionality supported by the different resources will now be discussedvia flowcharts in FIGS. 8, 9, and 10. Note that the steps in theflowcharts below can be executed in any suitable order.

FIG. 8 is a flowchart 800 illustrating an example method according toembodiments. Note that there will be some overlap with respect toconcepts as discussed above.

In processing block 810, the controller 140 controls magnitudes ofpressure in a first volume (such as chamber 150) and a second volume(such as chamber 130-2). The first volume is of a known magnitude (i.e.,size). The second volume is of an unknown magnitude (i.e., size).

In processing block 820, the controller 140 estimates a temperature ofgas in the first volume and a temperature of gas in the second volumebased on measurements of pressure in the first volume and measurementsof pressure in the second volume.

In processing block 830, the controller 140 calculates a magnitude ofthe second volume based on measured pressures of the gases and estimatedtemperatures of gases in the first volume and the second volume.

FIG. 9 is a flowchart 900 illustrating an example method according toembodiments. Note that there will be some overlap with respect toconcepts as discussed above.

In processing block 910, the controller 140 draws fluid into a chamberof a diaphragm pump 130.

In processing block 920, during a delivery phase, the controller 140applies pressure to the chamber 130-1. The applied pressure pumps thefluid in the chamber 130-1 to a target recipient 108.

In processing block 930, at multiple different times during the deliveryphase, the controller 140 temporarily discontinues application of thepressure to the chamber 130-2 to calculate how much of the fluid in thechamber 130-1 has been pumped to the target recipient 108.

FIG. 10 is a flowchart 1000 illustrating an example method according toembodiments. Note that there will be some overlap with respect toconcepts as discussed above.

In processing block 1010, the controller 140 controls magnitudes ofpressure in a first volume (such as chamber 150) and a second volume(such as chamber 130-2) to be dissimilar. The first volume is of knownmagnitude. The second volume is of unknown magnitude.

In processing block 1020, the controller 140 initiates opening a valve160-5 (while other valves are closed) between the first volume and thesecond volume to equalize a pressure in the first volume and the secondvolume.

In processing block 1030, the controller 140 estimates a temperature ofgas in the first volume and a temperature of gas in the second volumebased on a measured pressure in the first volume and measured pressureof the second volume.

In processing block 1040, the controller 140 calculates a magnitude ofthe second volume based on measured pressures of the gases and estimatedtemperatures of the gases in the first volume and the second volume.

Note again that techniques herein are well suited for use in fluiddelivery systems. However, it should be noted that embodiments hereinare not limited to use in such applications and that the techniquesdiscussed herein are well suited for other applications as well.

Based on the description set forth herein, numerous specific detailshave been set forth to provide a thorough understanding of claimedsubject matter. However, it will be understood by those skilled in theart that claimed subject matter may be practiced without these specificdetails. In other instances, methods, apparatuses, systems, etc., thatwould be known by one of ordinary skill have not been described indetail so as not to obscure claimed subject matter. Some portions of thedetailed description have been presented in terms of algorithms orsymbolic representations of operations on data bits or binary digitalsignals stored within a computing system memory, such as a computermemory. These algorithmic descriptions or representations are examplesof techniques used by those of ordinary skill in the data processingarts to convey the substance of their work to others skilled in the art.An algorithm as described herein, and generally, is considered to be aself-consistent sequence of operations or similar processing leading toa desired result. In this context, operations or processing involvephysical manipulation of physical quantities. Typically, although notnecessarily, such quantities may take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared orotherwise manipulated. It has been convenient at times, principally forreasons of common usage, to refer to such signals as bits, data, values,elements, symbols, characters, terms, numbers, numerals or the like. Itshould be understood, however, that all of these and similar terms areto be associated with appropriate physical quantities and are merelyconvenient labels. Unless specifically stated otherwise, as apparentfrom the following discussion, it is appreciated that throughout thisspecification discussions utilizing terms such as “processing,”“computing,” “calculating,” “determining” or the like refer to actionsor processes of a computing platform, such as a computer or a similarelectronic computing device, that manipulates or transforms datarepresented as physical electronic or magnetic quantities withinmemories, registers, or other information storage devices, transmissiondevices, or display devices of the computing platform.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of the presentapplication as defined by the appended claims. Such variations areintended to be covered by the scope of this present application. Assuch, the foregoing description of embodiments of the presentapplication is not intended to be limiting. Rather, any limitations tothe invention are presented in the following claims.

We claim:
 1. A method comprising: drawing fluid into a chamber of adiaphragm pump; during a delivery phase, applying pressure to thechamber, the applied pressure pumping the fluid in the chamber to atarget recipient; and at multiple different times during the deliveryphase, temporarily discontinuing application of the pressure to thechamber to calculate how much of the fluid in the chamber has beenpumped to the target recipient, the method further comprising:calculating an amount of fluid in the chamber at the multiple differenttimes during the delivery phase; and calculating a flow rate ofdelivering the fluid in the chamber to the target recipient based on thecalculated amount of fluid in the chamber at the multiple differenttimes during the delivery phase.
 2. The method as in claim 1, whereinapplying pressure to the chamber includes: applying a substantiallyconstant pressure to the chamber to evacuate the fluid from the chamberinto a conduit that conveys the fluid to the target recipient.
 3. Themethod as in claim 1 further comprising: comparing the calculated flowrate to a desired flow rate; and in response to detecting that adifference between the calculated flow rate and the desired flow rate isgreater than a threshold value, adjusting a flow rate of the fluid fromthe chamber to the target recipient to be nearer to the desired flowrate.
 4. The method as in claim 3, wherein adjusting the flow rateincludes: adjusting a magnitude of the pressure applied to the chamberduring the delivery phase.
 5. The method as in claim 4, whereinadjusting the flow rate includes: adjusting resistance of an in-lineflow resistor disposed between the chamber and the target recipient. 6.The method as in claim 1, wherein discontinuing application of thepressure to the chamber causes a pumping of the fluid in the chamber tothe recipient to substantially stop.
 7. The method as in claim 1 furthercomprising: subsequent to discontinuing application of the pressure tothe chamber, resuming application of the pressure to the chamber,resumption of applying the pressure causing the fluid in the chamber toflow to the recipient again.
 8. The method as in claim 1, whereindiscontinuing application of the pressure to the chamber includescontrolling magnitudes of pressure in the chamber and a gas reservoirtank to be dissimilar, a volume of the reservoir tank being of a knownmagnitude, a volume of the chamber being of an unknown magnitude, themethod further comprising: opening a valve between the reservoir tankand the chamber to substantially equalize a pressure of gas in thereservoir tank and the chamber; estimating a temperature of gas in thereservoir tank and a temperature of gas in the chamber based on ameasured pressure in the reservoir tank and measured pressure of thechamber; and calculating how much of the fluid remains in the chamberbased at least in part on measured pressures of the gases and theestimated temperatures of the gases in the reservoir tank and thechamber.
 9. A method comprising: drawing fluid into a chamber of adiaphragm pump; during a delivery phase, applying pressure to thechamber, the applied pressure pumping the fluid in the chamber to atarget recipient; and at multiple different times during the deliveryphase, temporarily discontinuing application of the pressure to thechamber to calculate how much of the fluid in the chamber has beenpumped to the target recipient; wherein discontinuing application of thepressure to the chamber includes controlling magnitudes of pressure inthe chamber and a gas reservoir tank to be dissimilar, a volume of thereservoir tank being of a known magnitude, a volume of the chamber beingof an unknown magnitude, the method further comprising: opening a valvebetween the reservoir tank and the chamber to substantially equalize apressure of gas in the reservoir tank and the chamber; estimating atemperature of gas in the reservoir tank and a temperature of gas in thechamber based on a measured pressure in the reservoir tank and measuredpressure of the chamber; and calculating how much of the fluid remainsin the chamber based at least in part on measured pressures of the gasesand the estimated temperatures of the gases in the reservoir tank andthe chamber.
 10. The method as in claim 9 further comprising:calculating how much of the fluid has been pumped to the targetrecipient based at least in part on how much of the fluid drawn into thechamber remains in the chamber after applying the pressure.
 11. Themethod as in claim 9, wherein applying pressure to the chamber includes:applying a substantially constant pressure to the chamber to evacuatethe fluid from the chamber into a conduit that conveys the fluid to thetarget recipient.
 12. The method as in claim 9, wherein discontinuingapplication of the pressure to the chamber causes a pumping of the fluidin the chamber to the recipient to substantially stop.
 13. The method asin claim 9 further comprising: subsequent to discontinuing applicationof the pressure to the chamber, resuming application of the pressure tothe chamber, resumption of applying the pressure causing the fluid inthe chamber to flow to the recipient again.
 14. A fluid delivery systemcomprising: a diaphragm pump; and a controller in controllablecommunication with the diaphragm pump, the controller operable to: drawfluid into a chamber of the diaphragm pump; during a delivery phase,apply pressure to the chamber, the applied pressure pumping the fluid inthe chamber to a target recipient; and at multiple different timesduring the delivery phase, temporarily discontinue application of thepressure to the chamber to calculate how much of the fluid in thechamber has been pumped to the target recipient; calculate an amount offluid in the chamber at the multiple different times during the deliveryphase; and calculate a flow rate of delivering the fluid in the chamberto the target recipient based on the calculated amount of fluid in thechamber at the multiple different times during the delivery phase. 15.The fluid delivery system as in claim 14, wherein the controller isfurther operable to: apply a substantially constant pressure to thechamber to evacuate the fluid from the chamber into a conduit thatconveys the fluid to the target recipient.
 16. The fluid delivery systemas in claim 14, wherein the controller is further operable to: comparethe calculated flow rate to a desired flow rate; and in response todetecting that a difference between the calculated flow rate and thedesired flow rate is greater than a threshold value, adjust a flow rateof the fluid from the chamber to the target recipient to be nearer tothe desired flow rate.
 17. The fluid delivery system as in claim 16,wherein the controller is further operable to: adjust a magnitude of thepressure applied to the chamber during the delivery phase.
 18. The fluiddelivery system as in claim 17, wherein the controller is furtheroperable to: adjust resistance of an in-line flow resistor disposedbetween the chamber and the target recipient.
 19. The fluid deliverysystem as in claim 14 further comprising: a gas reservoir tank; a valvedisposed between the chamber and the gas reservoir tank; and wherein thecontroller is further operable to: control magnitudes of pressure in thechamber and the gas reservoir tank to be dissimilar, a volume of the gasreservoir tank being of a known magnitude, a volume of the chamber beingof an unknown magnitude; open the valve between the gas reservoir tankand the chamber to substantially equalize a pressure of gas in the gasreservoir tank and the chamber; estimate a temperature of gas in the gasreservoir tank and a temperature of gas in the chamber based on ameasured pressure in the gas reservoir tank and measured pressure of thechamber; and calculate how much of the fluid remains in the chamberbased at least in part on measured pressures of the gases and theestimated temperatures of the gases in the gas reservoir tank and thechamber.
 20. The fluid delivery system as in claim 19, wherein thecontroller is further operable to: calculate how much of the fluid hasbeen pumped to the target recipient based at least in part on how muchof the fluid drawn into the chamber remains in the chamber afterapplying the pressure.
 21. The fluid delivery system as in claim 14,wherein the controller is further operable to discontinue application ofthe pressure to the chamber to substantially stop a pumping of the fluidin the chamber to the recipient.
 22. The fluid delivery system as inclaim 14, wherein the controller is further operable to: subsequent todiscontinuing application of the pressure to the chamber, resumeapplication of the pressure to the chamber, resumption of applying thepressure causing the fluid in the chamber to flow to the recipientagain.
 23. Computer-readable hardware storage having instructions storedthereon, the instructions, when carried out by computer processorhardware, causes the computer processor hardware to perform operationsof: drawing fluid into a chamber of a diaphragm pump; during a deliveryphase, applying pressure to the chamber, the applied pressure pumpingthe fluid in the chamber to a target recipient; and at multipledifferent times during the delivery phase, temporarily discontinuingapplication of the pressure to the chamber to calculate how much of thefluid in the chamber has been pumped to the target recipient;calculating an amount of fluid in the chamber at the multiple differenttimes during the delivery phase; and calculating a flow rate ofdelivering the fluid in the chamber to the target recipient based on thecalculated amount of fluid in the chamber at the multiple differenttimes during the delivery phase.
 24. A fluid delivery system comprising:a diaphragm pump including a chamber; a gas reservoir tank; a valvedisposed between the chamber and the gas reservoir tank and a controllerin controllable communication with the diaphragm pump, the controlleroperable to: draw fluid into the chamber of the diaphragm pump; during adelivery phase, apply pressure to the chamber, the applied pressurepumping the fluid in the chamber to a target recipient; and at multipledifferent times during the delivery phase, temporarily discontinueapplication of the pressure to the chamber to calculate how much of thefluid in the chamber has been pumped to the target recipient; whereinthe controller is further operable to: control magnitudes of pressure inthe chamber and the gas reservoir tank to be dissimilar, a volume of thegas reservoir tank being of a known magnitude, a volume of the chamberbeing of an unknown magnitude; open the valve between the gas reservoirtank and the chamber to substantially equalize a pressure of gas in thegas reservoir tank and the chamber; estimate a temperature of gas in thegas reservoir tank and a temperature of gas in the chamber based on ameasured pressure in the gas reservoir tank and measured pressure of thechamber; and calculate how much of the fluid remains in the chamberbased at least in part on measured pressures of the gases and theestimated temperatures of the gases in the gas reservoir tank and thechamber.
 25. The fluid delivery system as in claim 24, wherein thecontroller is further operable to: apply a substantially constantpressure to the chamber to evacuate the fluid from the chamber into aconduit that conveys the fluid to the target recipient.
 26. The fluiddelivery system as in claim 24, wherein discontinuing application of thepressure to the chamber causes a pumping of the fluid in the chamber tothe recipient to substantially stop.
 27. The fluid delivery system as inclaim 24, wherein the controller is further operable to: subsequent todiscontinuing application of the pressure to the chamber, resumeapplication of the pressure to the chamber, resumption of applying thepressure causing the fluid in the chamber to flow to the recipientagain.